Subjects will be excluded if they are receiving corticosteroids or antihypertensive medications; another current Axis I psychiatric disorder; a neurological or medically unstable condition; substance or alcohol misuse in the past 3 months; or electroconvulsive therapy in the last year. Other exclusion criteria include the presence of diabetes mellitus or hyperglycemia, BMI equal or greater than 40 kg/m^2 or inability to provide written informed consent. Patients who are actively suicidal or evaluated as being a suicide risk will be excluded. Other reasons for discontinuation are voluntary discontinuation, failure to complete 1 month of euthymia, impaired fasting glucose (i.e. 6.1-6.9 mmol/L), non-compliance (i.e. failure to administer > 80% of the assigned treatment in any week). Insulin will be measured quantitatively on a weekly basis; subjects will also complete a diary of when they took intranasal insulin and their prescribed medication.